Carbohydrates Classification and Examples

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Questions and Answers

What type of linkage is primarily found in amylose?

α-1,4 linkage (correct)

β-1,4 linkage

γ-1,4 linkage

α-1,6 linkage

Which polysaccharide serves as a storage form of glucose in animals?

Chitin

Starch

Cellulose

Glycogen (correct)

Which structural polysaccharide is primarily composed of β-(1-4) glycosidic linkages?

Inulin

Glycogen

Starch

Chitin (correct)

What is the primary use of cellulose in the human diet?

Acts as a ruffage Signup and view all the answers

What elements primarily make up carbohydrates?

Carbon, hydrogen, and oxygen Signup and view all the answers

Which feature distinguishes glycogen from starch?

Branching frequency Signup and view all the answers

What is the primary function of glycosidic bonds in carbohydrates?

To join monosaccharides Signup and view all the answers

What is the main building block of chitin?

N-acetylglucosamine Signup and view all the answers

Where is cellulose most commonly found in nature?

Plant cell walls Signup and view all the answers

What distinguishes an O-glycosidic bond from an N-glycosidic bond?

The non-carbohydrate group attached Signup and view all the answers

Which of the following accurately describes inulin?

A long chain of D-fructose with β-1,2 linkages Signup and view all the answers

What is the general formula for carbohydrates?

Cx(H2O)y Signup and view all the answers

Which common carbohydrate is a disaccharide of physiological significance?

Maltose Signup and view all the answers

What is the significance of pentoses in human metabolism?

They are used to form genetic material Signup and view all the answers

Which of the following best describes glycoside formation?

It occurs through the interaction of hydroxyl groups Signup and view all the answers

Which of the following carbohydrates is classified as a hexose?

Fructose Signup and view all the answers

What is the main function of phosphorylating glycolytic intermediates?

To lower their activation energy for enzymatic reactions Signup and view all the answers

Which of the following substances inhibits pyruvate kinase activity?

Fatty acids Signup and view all the answers

In which situation is anaerobic glycolysis primarily utilized?

During high-intensity exercise Signup and view all the answers

What role do cofactors like K+ and Mg2+ play in pyruvate kinase activity?

They stabilize the active site of the enzyme Signup and view all the answers

Which pathway involves the conversion of pyruvate to lactate?

Anaerobic glycolysis Signup and view all the answers

What is the role of aldose reductase in the metabolism of glucose?

Forms sorbitol from glucose. Signup and view all the answers

Which enzyme is responsible for converting sorbitol to D-fructose in certain tissues?

Sorbitol dehydrogenase Signup and view all the answers

What metabolic defect is caused by a deficiency in fructokinase?

Essential fructosuria Signup and view all the answers

Which product is formed when lactose is hydrolyzed?

Glucose and galactose Signup and view all the answers

What is the consequence of the absence of aldolase B in metabolism?

Severe hypoglycemia and jaundice Signup and view all the answers

UDP-galactose is primarily used for which of the following?

Formation of glycogen and glycoproteins Signup and view all the answers

Which condition results from a deficiency in galactokinase?

Non-classical galactosemia Signup and view all the answers

What is a consequence of lactose intolerance?

Deficiency of β-galactosidase Signup and view all the answers

What is the overall reaction when pyruvate is converted to Acetyl CoA?

Pyruvate + NAD+ + CoASH → Acetyl CoA + NADH + H+ + CO2 Signup and view all the answers

Which factor increases the activity of pyruvate dehydrogenase (PDH) according to the regulatory mechanisms?

Increased insulin levels Signup and view all the answers

Which enzyme is key in the oxidative decarboxylation of isocitrate?

Isocitrate dehydrogenase Signup and view all the answers

What is produced along with NADH during the conversion of α-ketoglutarate to succinyl CoA?

CO2 Signup and view all the answers

What role does citrate play in its own synthesis reaction?

Inhibitor of citrate synthase Signup and view all the answers

Which of the following coenzymes is required by the pyruvate dehydrogenase complex?

CoA Signup and view all the answers

What type of phosphorylation occurs during the cleavage of Succinyl CoA?

Substrate-level phosphorylation Signup and view all the answers

How many ATPs are generated from the oxidation of malate to oxaloacetate?

3 ATPs Signup and view all the answers

What is the primary role of hexokinase in glucose metabolism?

Converts glucose to glucose 6-phosphate Signup and view all the answers

What distinguishes glucokinase from hexokinase?

Glucokinase operates at high glucose levels. Signup and view all the answers

Which enzyme is responsible for the conversion of fructose 1,6-bisphosphate into triose phosphates?

Aldolase Signup and view all the answers

What effect does ATP have on the enzyme phosphofructokinase I (PFK I)?

Inhibits PFK I Signup and view all the answers

What is the main purpose of the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

To oxidize glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate Signup and view all the answers

What occurs during the conversion of 2-phosphoglycerate to phosphoenolpyruvate?

Reversible reaction catalyzed by enolase Signup and view all the answers

Which molecule does phophoglycerate mutase act upon?

3-phosphoglycerate Signup and view all the answers

What is the role of fluoride in the context of the glycolytic pathway?

Inhibits enolase Signup and view all the answers

Study Notes

Carbohydrates

Carbohydrates are polyhydroxy aldehydes or ketones and their derivatives.
They consist of carbon (C), hydrogen (H), and oxygen (O) atoms.
They are represented by the general formula C_x(H₂O)_y.
"Saccharide" comes from Greek, Sanskrit, and Latin words for table sugar.

Classification of Carbohydrates

Monosaccharides: Classified based on the number of carbon atoms (trioses, tetroses, pentoses, hexoses, heptoses). Further classified as aldoses or ketoses based on functional groups.
Oligosaccharides: Contain 2 to 10 monosaccharide units.
- Disaccharides (two monosaccharides)
- Trisaccharides (three monosaccharides)
- Etc.
Polysaccharides: Composed of many monosaccharides.
- Homo-polysaccharides: Composed of the same type of monosaccharides.
- Hetero-polysaccharides: Composed of different types of monosaccharides.

Examples of Monosaccharides

Trioses: Glyceraldehyde, dihydroxyacetone
Tetroses: D-erythrose
Pentoses: D-ribose, D-glucose, D-fructose
Hexoses: D-glucose, D-fructose, D-galactose, D-mannose
Importance: Building blocks of other carbohydrates, structural components in nucleic acids, and primary energy source

Examples of Disaccharides

Sucrose: Glucose + Fructose
Lactose: Glucose + Galactose
Maltose: Glucose + Glucose
Isomaltose: Glucose + Glucose (different linkage than maltose)
Clinical Significance: Sucrose intolerance, lactose intolerance

Examples of Polysaccharides

Starch: Storage form of glucose in plants, important in food.
Glycogen: Storage form of glucose in animals, stored in liver and muscle.
Cellulose: Structural component of plant cell walls (important dietary fiber).
Chitin: Structural component of fungal cell walls and insect exoskeletons.
Dextran: Polysaccharide of glucose varying chain length.

Glycosidic Bonds

Bonds between monosaccharides.
Two types: O-glycosidic and N-glycosidic bonds
Formed when hydroxyl group on one monosaccharide reacts with the hydroxyl group of another.

Cellular Respiration

Glycolysis: Breakdown of glucose to pyruvate or lactate (cytosolic).
Citric Acid Cycle (TCA cycle): Further breakdown of pyruvate to Acetyl CoA.
Oxidative Phosphorylation: Generating most of the ATP in the mitochondria from reduced electron carriers.

Metabolic Fate of Pyruvate

Pyruvate can be transformed to Acetyl CoA, which is a major building block in the TCA cycle
Pyruvate can also be converted to lactate by lactate dehydrogenase, crucial for anaerobic conditions.
Pyruvate can also be converted to oxaloacetate by pyruvate carboxylase important for replenishing citric acid intermediates.

TCA Cycle

Acetyl CoA enters the TCA cycle.
Series of reactions leading to the oxidation of acetyl CoA to CO₂.
Important for energy production.
Important intermediate for synthesis of fatty amino acids and other biomolecules.

Metabolism of Fructose

Fructose, a component of sucrose.
Metabolism occurs in the liver, intestinal mucosa, and kidneys.
Phosphorylation by fructokinase, the major mechanism.
Cleaved to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate, which enter glycolysis.
Sorbitol pathway for fructose synthesis.

Metabolism of Galactose

Lactose hydrolysis produces glucose and galactose.
Galactose phosphorylated to galactose-1-phosphate, then to UDP-galactose.
UDP-galactose converted back to UDP-glucose, enters various pathways.
Galactose also used to synthesize other molecules.

Disorders

Defects in glycolytic enzymes can lead to various diseases and complications.
Common defects include those in hexokinase, phosphofructokinase, and pyruvate kinase.
There have also been described defects in the TCA cycle enzymes and pathways

Alcohol Metabolism

Alcohol converted to acetaldehyde by alcohol dehydrogenase
Acetaldehyde converted to acetate by aldehyde dehydrogenase
NADH levels increase, affecting the balance of pyruvate, lactate, and oxaloacetate -Alcohol's effects on metabolism can lead to hypoglycemia.

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Description

Explore the fascinating world of carbohydrates, their classifications, and examples. This quiz covers monosaccharides, oligosaccharides, and polysaccharides, including specific types like trioses and disaccharides. Test your knowledge on the chemical structures and classifications of these essential biomolecules.